Continuous research has been underway in the vehicle industry in order to suppress generation of CO2 and improve fuel efficiency. For this purpose, efforts to replace metal components of vehicles with polymer composites have been continuously made. For instance, carbon fiber composites exhibit excellent electrical, thermal and mechanical properties, thus being studied for a variety of applications from the vehicle industry to aerospace.
Carbon fibers are subjected to a final process, surface-treatment, called “sizing”, to prevent damage of fibers by friction, improve wettability with thermosetting resins and reduce surface pores in the process of manufacturing. During sizing, the interfacial bonding force with a thermosetting resin such as epoxy may be improved, however, mechanical properties and the like may not be obtained due to bad compatibility with a general thermoplastic resin, e.g., a highly hydrophobic polymer. Accordingly, polymer composites may be reinforced with glass fibers. As such, surface-treatment and compatibility with most polymers may be easily obtained for use in various industries, however, carbon fibers may have limited application to highly hydrophilic polymers such as nylon.
In the related art, disclosed is carbon fibers that are surface-treated using UV-ozone, and the surfaces of carbon fibers are functionalized again with an interfacial bonding agent to improve bonding strength with the resin matrix.
In addition, in the related art, carbon fibers may be treated with nitric acid, a silane-based interfacial bonding agent may be added thereto and the resulting mixture may be mixed with a thermoplastic polymer such as polypropylene to improve bonding strength between the two ingredients.
Likewise, in the related art, pretreatment to remove the sizing agent attached to the surfaces of carbon fibers by treatment with an acid or base, or ozone or plasma, may be conducted and the carbon fibers may be mixed with a polymer to improve bonding strength between carbon fibers and the polymer. However, this pretreatment step may be very dangerous, eliminate inherent properties of carbon fibers and produce a substantial amount of waste after surface-treatment.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the related art.